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  <h1>常见的编程语言</h1>
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     ul, body, h1, p 这些标签的默认样式都是有的
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      ul 标签的默认样式是：
      list-style-type: disc;
        list-style-type: circle;
        list-style-type: square;
        list-style-type: none;
        list-style-type: decimal;
        list-style-type: decimal-leading-zero;
        list-style-type: lower-roman;
        list-style-type: upper-roman;

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  <ul>
    <li>
      <span>1</span>
      JavaScript
    </li>
    <li>Java</li>
    <li>C++</li>
    <li>Objective-C</li>
    <li>Swift</li>
    <li>Ruby</li>
    <li>Python</li>
  </ul>

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